Every time a page is opened on my site we update the row of that page in the database with an additional view:

PHP Code:
$addview mysql_query("UPDATE video SET views=views+1 WHERE video_id=$videoid LIMIT 1",$cont); 
We've never really had an issue with MySQL skying our loads or slowing page views. Here is an example of a busy day (w/loadavg):

Okay, not too bad. Now, only recently have been having weird load issues. Our tech says it's because we're updating the "views" column so often, but we've been three times as busy and never had issues with table locking before. Here is our load graphs today, and notice we are less than 2/3rds as busy as the day with good loads:

The weird part is, notice that the load drops at the start of each new hour? I have no cron running at the beginning of each hour. What can be causing these timed drops in load?